From the snapshot notes:
- Stalactites drip water (or lava if there is lava above the ceiling)
- A stalactite with a water source above the ceiling will gradually fill a cauldron below with water
- A stalactite with a lava source above the ceiling will fill a cauldron below with lava after a while
Stalactites drops water/lava bellow them if there is water/lava above their ceiling
But they only fill cauldron if the Stalactites is exactly 1 block high. If the stalactite is 2 blocks or bigger they drop lava/water but it won't fill cauldrons.
Tested with Lava and Water using full sources (non flowing).
drops coming from Stalactites should fill cauldron no matter their height.